1 /* 2 * This file contains the procedures for the handling of select and poll 3 * 4 * Created for Linux based loosely upon Mathius Lattner's minix 5 * patches by Peter MacDonald. Heavily edited by Linus. 6 * 7 * 4 February 1994 8 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS 9 * flag set in its personality we do *not* modify the given timeout 10 * parameter to reflect time remaining. 11 * 12 * 24 January 2000 13 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 14 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian). 15 */ 16 17 #include <linux/kernel.h> 18 #include <linux/sched.h> 19 #include <linux/syscalls.h> 20 #include <linux/export.h> 21 #include <linux/slab.h> 22 #include <linux/poll.h> 23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */ 24 #include <linux/file.h> 25 #include <linux/fdtable.h> 26 #include <linux/fs.h> 27 #include <linux/rcupdate.h> 28 #include <linux/hrtimer.h> 29 #include <linux/sched/rt.h> 30 31 #include <asm/uaccess.h> 32 33 34 /* 35 * Estimate expected accuracy in ns from a timeval. 36 * 37 * After quite a bit of churning around, we've settled on 38 * a simple thing of taking 0.1% of the timeout as the 39 * slack, with a cap of 100 msec. 40 * "nice" tasks get a 0.5% slack instead. 41 * 42 * Consider this comment an open invitation to come up with even 43 * better solutions.. 44 */ 45 46 #define MAX_SLACK (100 * NSEC_PER_MSEC) 47 48 static long __estimate_accuracy(struct timespec *tv) 49 { 50 long slack; 51 int divfactor = 1000; 52 53 if (tv->tv_sec < 0) 54 return 0; 55 56 if (task_nice(current) > 0) 57 divfactor = divfactor / 5; 58 59 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) 60 return MAX_SLACK; 61 62 slack = tv->tv_nsec / divfactor; 63 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); 64 65 if (slack > MAX_SLACK) 66 return MAX_SLACK; 67 68 return slack; 69 } 70 71 long select_estimate_accuracy(struct timespec *tv) 72 { 73 unsigned long ret; 74 struct timespec now; 75 76 /* 77 * Realtime tasks get a slack of 0 for obvious reasons. 78 */ 79 80 if (rt_task(current)) 81 return 0; 82 83 ktime_get_ts(&now); 84 now = timespec_sub(*tv, now); 85 ret = __estimate_accuracy(&now); 86 if (ret < current->timer_slack_ns) 87 return current->timer_slack_ns; 88 return ret; 89 } 90 91 92 93 struct poll_table_page { 94 struct poll_table_page * next; 95 struct poll_table_entry * entry; 96 struct poll_table_entry entries[0]; 97 }; 98 99 #define POLL_TABLE_FULL(table) \ 100 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) 101 102 /* 103 * Ok, Peter made a complicated, but straightforward multiple_wait() function. 104 * I have rewritten this, taking some shortcuts: This code may not be easy to 105 * follow, but it should be free of race-conditions, and it's practical. If you 106 * understand what I'm doing here, then you understand how the linux 107 * sleep/wakeup mechanism works. 108 * 109 * Two very simple procedures, poll_wait() and poll_freewait() make all the 110 * work. poll_wait() is an inline-function defined in <linux/poll.h>, 111 * as all select/poll functions have to call it to add an entry to the 112 * poll table. 113 */ 114 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 115 poll_table *p); 116 117 void poll_initwait(struct poll_wqueues *pwq) 118 { 119 init_poll_funcptr(&pwq->pt, __pollwait); 120 pwq->polling_task = current; 121 pwq->triggered = 0; 122 pwq->error = 0; 123 pwq->table = NULL; 124 pwq->inline_index = 0; 125 } 126 EXPORT_SYMBOL(poll_initwait); 127 128 static void free_poll_entry(struct poll_table_entry *entry) 129 { 130 remove_wait_queue(entry->wait_address, &entry->wait); 131 fput(entry->filp); 132 } 133 134 void poll_freewait(struct poll_wqueues *pwq) 135 { 136 struct poll_table_page * p = pwq->table; 137 int i; 138 for (i = 0; i < pwq->inline_index; i++) 139 free_poll_entry(pwq->inline_entries + i); 140 while (p) { 141 struct poll_table_entry * entry; 142 struct poll_table_page *old; 143 144 entry = p->entry; 145 do { 146 entry--; 147 free_poll_entry(entry); 148 } while (entry > p->entries); 149 old = p; 150 p = p->next; 151 free_page((unsigned long) old); 152 } 153 } 154 EXPORT_SYMBOL(poll_freewait); 155 156 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) 157 { 158 struct poll_table_page *table = p->table; 159 160 if (p->inline_index < N_INLINE_POLL_ENTRIES) 161 return p->inline_entries + p->inline_index++; 162 163 if (!table || POLL_TABLE_FULL(table)) { 164 struct poll_table_page *new_table; 165 166 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); 167 if (!new_table) { 168 p->error = -ENOMEM; 169 return NULL; 170 } 171 new_table->entry = new_table->entries; 172 new_table->next = table; 173 p->table = new_table; 174 table = new_table; 175 } 176 177 return table->entry++; 178 } 179 180 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 181 { 182 struct poll_wqueues *pwq = wait->private; 183 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); 184 185 /* 186 * Although this function is called under waitqueue lock, LOCK 187 * doesn't imply write barrier and the users expect write 188 * barrier semantics on wakeup functions. The following 189 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() 190 * and is paired with set_mb() in poll_schedule_timeout. 191 */ 192 smp_wmb(); 193 pwq->triggered = 1; 194 195 /* 196 * Perform the default wake up operation using a dummy 197 * waitqueue. 198 * 199 * TODO: This is hacky but there currently is no interface to 200 * pass in @sync. @sync is scheduled to be removed and once 201 * that happens, wake_up_process() can be used directly. 202 */ 203 return default_wake_function(&dummy_wait, mode, sync, key); 204 } 205 206 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 207 { 208 struct poll_table_entry *entry; 209 210 entry = container_of(wait, struct poll_table_entry, wait); 211 if (key && !((unsigned long)key & entry->key)) 212 return 0; 213 return __pollwake(wait, mode, sync, key); 214 } 215 216 /* Add a new entry */ 217 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 218 poll_table *p) 219 { 220 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 221 struct poll_table_entry *entry = poll_get_entry(pwq); 222 if (!entry) 223 return; 224 entry->filp = get_file(filp); 225 entry->wait_address = wait_address; 226 entry->key = p->_key; 227 init_waitqueue_func_entry(&entry->wait, pollwake); 228 entry->wait.private = pwq; 229 add_wait_queue(wait_address, &entry->wait); 230 } 231 232 int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 233 ktime_t *expires, unsigned long slack) 234 { 235 int rc = -EINTR; 236 237 set_current_state(state); 238 if (!pwq->triggered) 239 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 240 __set_current_state(TASK_RUNNING); 241 242 /* 243 * Prepare for the next iteration. 244 * 245 * The following set_mb() serves two purposes. First, it's 246 * the counterpart rmb of the wmb in pollwake() such that data 247 * written before wake up is always visible after wake up. 248 * Second, the full barrier guarantees that triggered clearing 249 * doesn't pass event check of the next iteration. Note that 250 * this problem doesn't exist for the first iteration as 251 * add_wait_queue() has full barrier semantics. 252 */ 253 set_mb(pwq->triggered, 0); 254 255 return rc; 256 } 257 EXPORT_SYMBOL(poll_schedule_timeout); 258 259 /** 260 * poll_select_set_timeout - helper function to setup the timeout value 261 * @to: pointer to timespec variable for the final timeout 262 * @sec: seconds (from user space) 263 * @nsec: nanoseconds (from user space) 264 * 265 * Note, we do not use a timespec for the user space value here, That 266 * way we can use the function for timeval and compat interfaces as well. 267 * 268 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 269 */ 270 int poll_select_set_timeout(struct timespec *to, long sec, long nsec) 271 { 272 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec}; 273 274 if (!timespec_valid(&ts)) 275 return -EINVAL; 276 277 /* Optimize for the zero timeout value here */ 278 if (!sec && !nsec) { 279 to->tv_sec = to->tv_nsec = 0; 280 } else { 281 ktime_get_ts(to); 282 *to = timespec_add_safe(*to, ts); 283 } 284 return 0; 285 } 286 287 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, 288 int timeval, int ret) 289 { 290 struct timespec rts; 291 struct timeval rtv; 292 293 if (!p) 294 return ret; 295 296 if (current->personality & STICKY_TIMEOUTS) 297 goto sticky; 298 299 /* No update for zero timeout */ 300 if (!end_time->tv_sec && !end_time->tv_nsec) 301 return ret; 302 303 ktime_get_ts(&rts); 304 rts = timespec_sub(*end_time, rts); 305 if (rts.tv_sec < 0) 306 rts.tv_sec = rts.tv_nsec = 0; 307 308 if (timeval) { 309 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 310 memset(&rtv, 0, sizeof(rtv)); 311 rtv.tv_sec = rts.tv_sec; 312 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 313 314 if (!copy_to_user(p, &rtv, sizeof(rtv))) 315 return ret; 316 317 } else if (!copy_to_user(p, &rts, sizeof(rts))) 318 return ret; 319 320 /* 321 * If an application puts its timeval in read-only memory, we 322 * don't want the Linux-specific update to the timeval to 323 * cause a fault after the select has completed 324 * successfully. However, because we're not updating the 325 * timeval, we can't restart the system call. 326 */ 327 328 sticky: 329 if (ret == -ERESTARTNOHAND) 330 ret = -EINTR; 331 return ret; 332 } 333 334 #define FDS_IN(fds, n) (fds->in + n) 335 #define FDS_OUT(fds, n) (fds->out + n) 336 #define FDS_EX(fds, n) (fds->ex + n) 337 338 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 339 340 static int max_select_fd(unsigned long n, fd_set_bits *fds) 341 { 342 unsigned long *open_fds; 343 unsigned long set; 344 int max; 345 struct fdtable *fdt; 346 347 /* handle last in-complete long-word first */ 348 set = ~(~0UL << (n & (BITS_PER_LONG-1))); 349 n /= BITS_PER_LONG; 350 fdt = files_fdtable(current->files); 351 open_fds = fdt->open_fds + n; 352 max = 0; 353 if (set) { 354 set &= BITS(fds, n); 355 if (set) { 356 if (!(set & ~*open_fds)) 357 goto get_max; 358 return -EBADF; 359 } 360 } 361 while (n) { 362 open_fds--; 363 n--; 364 set = BITS(fds, n); 365 if (!set) 366 continue; 367 if (set & ~*open_fds) 368 return -EBADF; 369 if (max) 370 continue; 371 get_max: 372 do { 373 max++; 374 set >>= 1; 375 } while (set); 376 max += n * BITS_PER_LONG; 377 } 378 379 return max; 380 } 381 382 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 383 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 384 #define POLLEX_SET (POLLPRI) 385 386 static inline void wait_key_set(poll_table *wait, unsigned long in, 387 unsigned long out, unsigned long bit) 388 { 389 wait->_key = POLLEX_SET; 390 if (in & bit) 391 wait->_key |= POLLIN_SET; 392 if (out & bit) 393 wait->_key |= POLLOUT_SET; 394 } 395 396 int do_select(int n, fd_set_bits *fds, struct timespec *end_time) 397 { 398 ktime_t expire, *to = NULL; 399 struct poll_wqueues table; 400 poll_table *wait; 401 int retval, i, timed_out = 0; 402 unsigned long slack = 0; 403 404 rcu_read_lock(); 405 retval = max_select_fd(n, fds); 406 rcu_read_unlock(); 407 408 if (retval < 0) 409 return retval; 410 n = retval; 411 412 poll_initwait(&table); 413 wait = &table.pt; 414 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 415 wait->_qproc = NULL; 416 timed_out = 1; 417 } 418 419 if (end_time && !timed_out) 420 slack = select_estimate_accuracy(end_time); 421 422 retval = 0; 423 for (;;) { 424 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 425 426 inp = fds->in; outp = fds->out; exp = fds->ex; 427 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 428 429 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 430 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 431 unsigned long res_in = 0, res_out = 0, res_ex = 0; 432 433 in = *inp++; out = *outp++; ex = *exp++; 434 all_bits = in | out | ex; 435 if (all_bits == 0) { 436 i += BITS_PER_LONG; 437 continue; 438 } 439 440 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { 441 struct fd f; 442 if (i >= n) 443 break; 444 if (!(bit & all_bits)) 445 continue; 446 f = fdget(i); 447 if (f.file) { 448 const struct file_operations *f_op; 449 f_op = f.file->f_op; 450 mask = DEFAULT_POLLMASK; 451 if (f_op && f_op->poll) { 452 wait_key_set(wait, in, out, bit); 453 mask = (*f_op->poll)(f.file, wait); 454 } 455 fdput(f); 456 if ((mask & POLLIN_SET) && (in & bit)) { 457 res_in |= bit; 458 retval++; 459 wait->_qproc = NULL; 460 } 461 if ((mask & POLLOUT_SET) && (out & bit)) { 462 res_out |= bit; 463 retval++; 464 wait->_qproc = NULL; 465 } 466 if ((mask & POLLEX_SET) && (ex & bit)) { 467 res_ex |= bit; 468 retval++; 469 wait->_qproc = NULL; 470 } 471 } 472 } 473 if (res_in) 474 *rinp = res_in; 475 if (res_out) 476 *routp = res_out; 477 if (res_ex) 478 *rexp = res_ex; 479 cond_resched(); 480 } 481 wait->_qproc = NULL; 482 if (retval || timed_out || signal_pending(current)) 483 break; 484 if (table.error) { 485 retval = table.error; 486 break; 487 } 488 489 /* 490 * If this is the first loop and we have a timeout 491 * given, then we convert to ktime_t and set the to 492 * pointer to the expiry value. 493 */ 494 if (end_time && !to) { 495 expire = timespec_to_ktime(*end_time); 496 to = &expire; 497 } 498 499 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 500 to, slack)) 501 timed_out = 1; 502 } 503 504 poll_freewait(&table); 505 506 return retval; 507 } 508 509 /* 510 * We can actually return ERESTARTSYS instead of EINTR, but I'd 511 * like to be certain this leads to no problems. So I return 512 * EINTR just for safety. 513 * 514 * Update: ERESTARTSYS breaks at least the xview clock binary, so 515 * I'm trying ERESTARTNOHAND which restart only when you want to. 516 */ 517 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 518 fd_set __user *exp, struct timespec *end_time) 519 { 520 fd_set_bits fds; 521 void *bits; 522 int ret, max_fds; 523 unsigned int size; 524 struct fdtable *fdt; 525 /* Allocate small arguments on the stack to save memory and be faster */ 526 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 527 528 ret = -EINVAL; 529 if (n < 0) 530 goto out_nofds; 531 532 /* max_fds can increase, so grab it once to avoid race */ 533 rcu_read_lock(); 534 fdt = files_fdtable(current->files); 535 max_fds = fdt->max_fds; 536 rcu_read_unlock(); 537 if (n > max_fds) 538 n = max_fds; 539 540 /* 541 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 542 * since we used fdset we need to allocate memory in units of 543 * long-words. 544 */ 545 size = FDS_BYTES(n); 546 bits = stack_fds; 547 if (size > sizeof(stack_fds) / 6) { 548 /* Not enough space in on-stack array; must use kmalloc */ 549 ret = -ENOMEM; 550 bits = kmalloc(6 * size, GFP_KERNEL); 551 if (!bits) 552 goto out_nofds; 553 } 554 fds.in = bits; 555 fds.out = bits + size; 556 fds.ex = bits + 2*size; 557 fds.res_in = bits + 3*size; 558 fds.res_out = bits + 4*size; 559 fds.res_ex = bits + 5*size; 560 561 if ((ret = get_fd_set(n, inp, fds.in)) || 562 (ret = get_fd_set(n, outp, fds.out)) || 563 (ret = get_fd_set(n, exp, fds.ex))) 564 goto out; 565 zero_fd_set(n, fds.res_in); 566 zero_fd_set(n, fds.res_out); 567 zero_fd_set(n, fds.res_ex); 568 569 ret = do_select(n, &fds, end_time); 570 571 if (ret < 0) 572 goto out; 573 if (!ret) { 574 ret = -ERESTARTNOHAND; 575 if (signal_pending(current)) 576 goto out; 577 ret = 0; 578 } 579 580 if (set_fd_set(n, inp, fds.res_in) || 581 set_fd_set(n, outp, fds.res_out) || 582 set_fd_set(n, exp, fds.res_ex)) 583 ret = -EFAULT; 584 585 out: 586 if (bits != stack_fds) 587 kfree(bits); 588 out_nofds: 589 return ret; 590 } 591 592 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 593 fd_set __user *, exp, struct timeval __user *, tvp) 594 { 595 struct timespec end_time, *to = NULL; 596 struct timeval tv; 597 int ret; 598 599 if (tvp) { 600 if (copy_from_user(&tv, tvp, sizeof(tv))) 601 return -EFAULT; 602 603 to = &end_time; 604 if (poll_select_set_timeout(to, 605 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 606 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 607 return -EINVAL; 608 } 609 610 ret = core_sys_select(n, inp, outp, exp, to); 611 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 612 613 return ret; 614 } 615 616 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 617 fd_set __user *exp, struct timespec __user *tsp, 618 const sigset_t __user *sigmask, size_t sigsetsize) 619 { 620 sigset_t ksigmask, sigsaved; 621 struct timespec ts, end_time, *to = NULL; 622 int ret; 623 624 if (tsp) { 625 if (copy_from_user(&ts, tsp, sizeof(ts))) 626 return -EFAULT; 627 628 to = &end_time; 629 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 630 return -EINVAL; 631 } 632 633 if (sigmask) { 634 /* XXX: Don't preclude handling different sized sigset_t's. */ 635 if (sigsetsize != sizeof(sigset_t)) 636 return -EINVAL; 637 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 638 return -EFAULT; 639 640 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 641 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 642 } 643 644 ret = core_sys_select(n, inp, outp, exp, to); 645 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 646 647 if (ret == -ERESTARTNOHAND) { 648 /* 649 * Don't restore the signal mask yet. Let do_signal() deliver 650 * the signal on the way back to userspace, before the signal 651 * mask is restored. 652 */ 653 if (sigmask) { 654 memcpy(¤t->saved_sigmask, &sigsaved, 655 sizeof(sigsaved)); 656 set_restore_sigmask(); 657 } 658 } else if (sigmask) 659 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 660 661 return ret; 662 } 663 664 /* 665 * Most architectures can't handle 7-argument syscalls. So we provide a 666 * 6-argument version where the sixth argument is a pointer to a structure 667 * which has a pointer to the sigset_t itself followed by a size_t containing 668 * the sigset size. 669 */ 670 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 671 fd_set __user *, exp, struct timespec __user *, tsp, 672 void __user *, sig) 673 { 674 size_t sigsetsize = 0; 675 sigset_t __user *up = NULL; 676 677 if (sig) { 678 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 679 || __get_user(up, (sigset_t __user * __user *)sig) 680 || __get_user(sigsetsize, 681 (size_t __user *)(sig+sizeof(void *)))) 682 return -EFAULT; 683 } 684 685 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 686 } 687 688 #ifdef __ARCH_WANT_SYS_OLD_SELECT 689 struct sel_arg_struct { 690 unsigned long n; 691 fd_set __user *inp, *outp, *exp; 692 struct timeval __user *tvp; 693 }; 694 695 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 696 { 697 struct sel_arg_struct a; 698 699 if (copy_from_user(&a, arg, sizeof(a))) 700 return -EFAULT; 701 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 702 } 703 #endif 704 705 struct poll_list { 706 struct poll_list *next; 707 int len; 708 struct pollfd entries[0]; 709 }; 710 711 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 712 713 /* 714 * Fish for pollable events on the pollfd->fd file descriptor. We're only 715 * interested in events matching the pollfd->events mask, and the result 716 * matching that mask is both recorded in pollfd->revents and returned. The 717 * pwait poll_table will be used by the fd-provided poll handler for waiting, 718 * if pwait->_qproc is non-NULL. 719 */ 720 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 721 { 722 unsigned int mask; 723 int fd; 724 725 mask = 0; 726 fd = pollfd->fd; 727 if (fd >= 0) { 728 struct fd f = fdget(fd); 729 mask = POLLNVAL; 730 if (f.file) { 731 mask = DEFAULT_POLLMASK; 732 if (f.file->f_op && f.file->f_op->poll) { 733 pwait->_key = pollfd->events|POLLERR|POLLHUP; 734 mask = f.file->f_op->poll(f.file, pwait); 735 } 736 /* Mask out unneeded events. */ 737 mask &= pollfd->events | POLLERR | POLLHUP; 738 fdput(f); 739 } 740 } 741 pollfd->revents = mask; 742 743 return mask; 744 } 745 746 static int do_poll(unsigned int nfds, struct poll_list *list, 747 struct poll_wqueues *wait, struct timespec *end_time) 748 { 749 poll_table* pt = &wait->pt; 750 ktime_t expire, *to = NULL; 751 int timed_out = 0, count = 0; 752 unsigned long slack = 0; 753 754 /* Optimise the no-wait case */ 755 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 756 pt->_qproc = NULL; 757 timed_out = 1; 758 } 759 760 if (end_time && !timed_out) 761 slack = select_estimate_accuracy(end_time); 762 763 for (;;) { 764 struct poll_list *walk; 765 766 for (walk = list; walk != NULL; walk = walk->next) { 767 struct pollfd * pfd, * pfd_end; 768 769 pfd = walk->entries; 770 pfd_end = pfd + walk->len; 771 for (; pfd != pfd_end; pfd++) { 772 /* 773 * Fish for events. If we found one, record it 774 * and kill poll_table->_qproc, so we don't 775 * needlessly register any other waiters after 776 * this. They'll get immediately deregistered 777 * when we break out and return. 778 */ 779 if (do_pollfd(pfd, pt)) { 780 count++; 781 pt->_qproc = NULL; 782 } 783 } 784 } 785 /* 786 * All waiters have already been registered, so don't provide 787 * a poll_table->_qproc to them on the next loop iteration. 788 */ 789 pt->_qproc = NULL; 790 if (!count) { 791 count = wait->error; 792 if (signal_pending(current)) 793 count = -EINTR; 794 } 795 if (count || timed_out) 796 break; 797 798 /* 799 * If this is the first loop and we have a timeout 800 * given, then we convert to ktime_t and set the to 801 * pointer to the expiry value. 802 */ 803 if (end_time && !to) { 804 expire = timespec_to_ktime(*end_time); 805 to = &expire; 806 } 807 808 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 809 timed_out = 1; 810 } 811 return count; 812 } 813 814 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 815 sizeof(struct pollfd)) 816 817 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 818 struct timespec *end_time) 819 { 820 struct poll_wqueues table; 821 int err = -EFAULT, fdcount, len, size; 822 /* Allocate small arguments on the stack to save memory and be 823 faster - use long to make sure the buffer is aligned properly 824 on 64 bit archs to avoid unaligned access */ 825 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 826 struct poll_list *const head = (struct poll_list *)stack_pps; 827 struct poll_list *walk = head; 828 unsigned long todo = nfds; 829 830 if (nfds > rlimit(RLIMIT_NOFILE)) 831 return -EINVAL; 832 833 len = min_t(unsigned int, nfds, N_STACK_PPS); 834 for (;;) { 835 walk->next = NULL; 836 walk->len = len; 837 if (!len) 838 break; 839 840 if (copy_from_user(walk->entries, ufds + nfds-todo, 841 sizeof(struct pollfd) * walk->len)) 842 goto out_fds; 843 844 todo -= walk->len; 845 if (!todo) 846 break; 847 848 len = min(todo, POLLFD_PER_PAGE); 849 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 850 walk = walk->next = kmalloc(size, GFP_KERNEL); 851 if (!walk) { 852 err = -ENOMEM; 853 goto out_fds; 854 } 855 } 856 857 poll_initwait(&table); 858 fdcount = do_poll(nfds, head, &table, end_time); 859 poll_freewait(&table); 860 861 for (walk = head; walk; walk = walk->next) { 862 struct pollfd *fds = walk->entries; 863 int j; 864 865 for (j = 0; j < walk->len; j++, ufds++) 866 if (__put_user(fds[j].revents, &ufds->revents)) 867 goto out_fds; 868 } 869 870 err = fdcount; 871 out_fds: 872 walk = head->next; 873 while (walk) { 874 struct poll_list *pos = walk; 875 walk = walk->next; 876 kfree(pos); 877 } 878 879 return err; 880 } 881 882 static long do_restart_poll(struct restart_block *restart_block) 883 { 884 struct pollfd __user *ufds = restart_block->poll.ufds; 885 int nfds = restart_block->poll.nfds; 886 struct timespec *to = NULL, end_time; 887 int ret; 888 889 if (restart_block->poll.has_timeout) { 890 end_time.tv_sec = restart_block->poll.tv_sec; 891 end_time.tv_nsec = restart_block->poll.tv_nsec; 892 to = &end_time; 893 } 894 895 ret = do_sys_poll(ufds, nfds, to); 896 897 if (ret == -EINTR) { 898 restart_block->fn = do_restart_poll; 899 ret = -ERESTART_RESTARTBLOCK; 900 } 901 return ret; 902 } 903 904 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 905 int, timeout_msecs) 906 { 907 struct timespec end_time, *to = NULL; 908 int ret; 909 910 if (timeout_msecs >= 0) { 911 to = &end_time; 912 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 913 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 914 } 915 916 ret = do_sys_poll(ufds, nfds, to); 917 918 if (ret == -EINTR) { 919 struct restart_block *restart_block; 920 921 restart_block = ¤t_thread_info()->restart_block; 922 restart_block->fn = do_restart_poll; 923 restart_block->poll.ufds = ufds; 924 restart_block->poll.nfds = nfds; 925 926 if (timeout_msecs >= 0) { 927 restart_block->poll.tv_sec = end_time.tv_sec; 928 restart_block->poll.tv_nsec = end_time.tv_nsec; 929 restart_block->poll.has_timeout = 1; 930 } else 931 restart_block->poll.has_timeout = 0; 932 933 ret = -ERESTART_RESTARTBLOCK; 934 } 935 return ret; 936 } 937 938 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 939 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 940 size_t, sigsetsize) 941 { 942 sigset_t ksigmask, sigsaved; 943 struct timespec ts, end_time, *to = NULL; 944 int ret; 945 946 if (tsp) { 947 if (copy_from_user(&ts, tsp, sizeof(ts))) 948 return -EFAULT; 949 950 to = &end_time; 951 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 952 return -EINVAL; 953 } 954 955 if (sigmask) { 956 /* XXX: Don't preclude handling different sized sigset_t's. */ 957 if (sigsetsize != sizeof(sigset_t)) 958 return -EINVAL; 959 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 960 return -EFAULT; 961 962 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 963 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 964 } 965 966 ret = do_sys_poll(ufds, nfds, to); 967 968 /* We can restart this syscall, usually */ 969 if (ret == -EINTR) { 970 /* 971 * Don't restore the signal mask yet. Let do_signal() deliver 972 * the signal on the way back to userspace, before the signal 973 * mask is restored. 974 */ 975 if (sigmask) { 976 memcpy(¤t->saved_sigmask, &sigsaved, 977 sizeof(sigsaved)); 978 set_restore_sigmask(); 979 } 980 ret = -ERESTARTNOHAND; 981 } else if (sigmask) 982 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 983 984 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 985 986 return ret; 987 } 988